Ganglioside metabolism will be correlated with structure and function in the hippocampus under precisely defined conditions of development and experimentally induced plasticity. The four phases of this study will consist of: I. Determination of optimal methods for microanalysis of ganglioside metabolism in minute tissue samples. II. Correlation of changes in ganglioside metabolism with precise morphogenetic events during the normal development of individual subfields of the hippocampus. III. Correlation of changes in ganglioside metabolism with structural plasticity in the hippocampus, experimentally induced by: A. kainic acid, to cause selective neuronal necrosis. B. Thyroxin, to cause ectopic axonal and terminal proliferation. IV. Correlation of changes in ganglioside metabolism with physiological modulation, experimentally induced by: A. chronic or acute corticosterone stimulation. B. noradrenergic denervation by 6-hydroxydopamine.